I'm curious if the weight difference is from a difference in the valve head/chamber side of the valves and/or a different shape/slope on the port side.
Over the years I've read that Mopar wedge engines tend to prefer flatter/nail-head intakes and more "tulip" shaped exhaust valves. But I'm sure that there might be other variables, not just an across-the-board standard.
Valve that are undercut in the stem for flow would be interesting to test also and would be saving weight too.